Asked how he would tackle North Korea, Trump said: “I’m not going to tell you. You know, I am not the United States of the past where we tell you where we are going to hit in the Middle East.”

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Trump will host the Chinese president, Xi Jinping, on Thursday and Friday at his Mar-a-Lago resort in Florida, where the two leaders are expected to discuss North Korea, China’s ambitions in the South China Sea and trade. There is speculation that North Korea could conduct another nuclear missile test to coincide with the talks.

Trump said he had “great respect” for Xi and “great respect for China”, adding: “I would not be at all surprised if we did something that would be very dramatic and good for both countries and I hope so.”

On North Korea, he said: “China has great influence over North Korea. And China will either decide to help us with North Korea, or they won’t. And if they do that will be very good for China, and if they don’t it won’t be good for anyone.”

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Asked what might motivate China to help, Trump said: “I think trade is the incentive. It is all about trade.”

Theresa May hinted that president Trump should re-think his “go it alone”approach to North Korea, saying the UK backed co-operation with Chinato de-escalate the situation.

Speaking after the US president said he was prepared to act without Chinese backing, the British prime minister said: “I think what is crucial, and where we have been working and will continue to work through the UN security council resolutions we’ve supported and with the United States is to encourage China to look at this issue of North Korea and play a more significant role in terms of North Korea, I think that’s where our attention should focus.”

Experts on the long standoff with North Korea, said there were few, if any, good options for acting without Chinese cooperation on the issue.

“There is no solving this problem ‘alone’”, said Jim Walsh, of MIT’s Security Studies Programme. “It would be unwise for the US to act unilaterally, without the support of its ally South Korea. And frankly, there is no resolving this peacefully without China. A sanctions strategy will not be effective without Beijing’s help, and threatening China to win their cooperation strikes me as a contradiction in terms. ”

Robert Kelly, a professor at Pusan National University in South Korea, was also sceptical about Trump’s ability to act on his own.

“America’s options are pretty poor, the North Koreans have been preparing for an American airstrike since the end of the Korean war in the 1950s,” he said. “They have been tunnelling for decades and have put a lot of strategic assets deep inside mountains. Any serious campaign would almost certainly not be surgical. It would take days, maybe weeks.”

“The United States will never be able to go it alone. Japan and South Korea are fundamental partners for deterrence, sanctions implementation, diplomatic moves--any tool the US could use to constrain [North Korea” Adam Mount, a North Korea specialist at the Centre for American Progress, said.

“Trump needs to learn to say this publicly, and to consult with allies from the start. Early administration statements have been vague, weak, and scattered. The White House should learn to rely on state for this kind of communication.”

China is seen as crucial to dealing with the threat of North Korea. It is the North’s main trading partner, providing much-needed foreign currency for the cash-strapped nation and the two share an 870-mile (1,400km) border. It has long provided diplomatic support in international forums, but denies it can fully control North Korea’s leader, Kim Jong-un.

The Trump administration got off to rocky start in its relations with Beijing with accusations from the president that Beijing has militarised the South China Sea, manipulated its currency and hampered attempts to rein in North Korea.

He also angered Beijing by hinting he could offer greater political recognition to Taiwan – a democratically ruled island that China claims as part of its own territory – though the White House later said Trump had agreed to honour Beijing’s One China policy.

China is reported to have developed a good relationship with Trump’s son-in-law, Jared Kushner, who plays a central role in the new administration. According to the New York Times, China’s ambassador to the US, Cui Tiankai, has been sharing draft statements with Kushner on what will be issued after the Mar-a-Lago talks.

Vivian Zhan, a politics professor at the Chinese University of Hong Kong, said China’s cooperation was key. “If the US could really take unilateral action against North Korea, it should have done so earlier, not waited until North Korea developed its nuclear programme and missiles to this extent,” said Zhan. “The US can’t really handle North Korea by itself. China has to be involved.”

The former head of British intelligence service MI6, Richard Dearlove, said the threat posed by North Korea should be a priority for the Trump administration.

In the latest episode of the podcast Talking Politics, recorded before Trump’s latest comments, Dearlove said: “We are in the middle of a policy one crisis which is North Korea. There is only one solution to dealing with the North Koreans, which is to secure the cooperation of the Chinese.”

In a separate conversation, Trump’s deputy national security adviser, KT McFarland, told the FT there was a “real possibility” North Korea could be capable of hitting the US with a nuclear-armed missile by the end of Trump’s first term. Intelligence experts disagree with McFarland’s assessment.

A Japanese government source with knowledge of the country’s North Korea policy pointed out that UN sanctions, multiparty talks and attempts to encourage Beijing to stop North Korea from from going nuclear “have all come to nought”.

The official told the Guardian: “The region is under a dramatically increased threat from Pyongyang, which now is gaining real first-strike capabilities. In these circumstances President Trump is right: it is high time for Washington to strongly urge Beijing to pull all possible strings to stop North Korea from advancing their nuclear ambitions, while seeking any means of their own to that same end.”